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Immulite chemiluminescent immunoassay for PTH in pediatric samples compared to Nichols Institute immunoradiometric assay
9TH INTERNATIONAL/6TH EUROPEAN JOINT SYMPOSIUM ON PURINE AND PYRIMIDINE METABOLISM IN MAN
23.
AUTOMATED ANALYSIS OF URINARY OXALATE USING BMC OXALATE DECARBOXYLASEBASED A S S A Y KIT Chu, SY, Biochemistry Laboratory, Dr. E. Chalmers Hospital, Fredericton, N.B. E3B 5N5
Increased oxalate excretion is commonly associated with u r i n a r y calculi formation. Oxalate determination based on a n enzymatic assay system offers assay simplicity and reliability. Objectives 1) To investigate the optimum assay conditions of the BMC oxalate decarboxylase method for urine oxalate determination; 2) To develop a n automated procedure on the Cobas Mira using the BMC kit. Methods Oxalate is first cleaved to formic acid by oxalate decarboxylase a n d subsequently the formic acid is quantitatively oxidized to bicarbonate in the presence of formate dehydrogenase. The a m o u n t of NADH formed during the reaction is m e a s u r e d by a n increase of OD at 340 nm. Optimal incubation time was followed by OD change at 37 ° after fixed incubation period for either the first stage or final stage of the reaction. Automated assay p a r a m e t e r s were developed based on optimal incubation time, sample reagent ratio, linearity range and m a x i m u m recovery. Results Five m i n u t e incubation time for both enzymatic reactions was chosen. A sample reagent ratio of 1:10 was used. Sample b l a n k was required to correct for endogenous non-specific O.D. change. EDTA was also required to improve sample oxalate recovery and to minimize oxalate precipitation. A 3% CV was obtained in pair data study and 6% CV for between day imprecision study. Linearity up to 1200 ~Lmol/L was obtained. Conclusion We have adopted the BMC oxalate test kit to be r u n on the Cobas Mira offering a fast and reliable procedure for u r i n a r y oxalic acid determination.
24.
IMMULITE CHEMILUMINESCENT IMMUNOASSAY FOR PTH IN PEDIATRIC SAMPLES COMPARED TO NICHOLS INSTITUTE IMMUNORADIOMETRIC A S S A Y Abdelrahman, A:~ Wan, B., Grossi, A., Makela, S., and Ellis, G., Paediatric Laboratory Medicine, Hospital for Sick Children, 555 University Avenue, Toronto, ONT M5G 1X8, Canada
Objective To compare the performance of the IMMULITE chemiluminescent i m m u n o a s s a y (IMM) for serum parathyroid hormone (PTH) to the Nichols Institute (NI) assay. Methods S e r u m PTH levels were m e a s u r e d by both methods in all samples received over a five m o n t h period (n = 366). When t h e r e was a large difference between the PTH values obtained by the two methods, we reviewed the p a t i e n t chart. Results There was a good correlation between both methods (IMM = 7.9 + 1.04NI, r = 0.969), however t h e r e were some large differences between values m e a s u r e d by the two methods for some of the samples as shown in the table: PTH (ng/L), total calcium (Ca, mmol/L), ionized calcium (ion. Ca, mmol/L).
PTH (NI)
PTH (IMM)
Ca
Ion. Ca
Diagnosis
1
1
20
2.89
1.26
Idiopathic hypercalcemia
2
22
981
2.54
1.17
Partial DiGeorge
3
2
22
2.77
NA
Hypercalcemia
4
10
36
2.55
1.09
Mild Partial DiGeorge
5
15
159
2.33
1.16
Developmental delay
6
32
5
2.74
1.28
E n d stage renal disease
374
Conclusions The exact reason for these differences in PTH values between the two methods was not clear even after reviewing the patients charts. However, caution m u s t be used when interpreting PTH results for some pediatric samples.
25.
EVALUATION OF ELECSYS--~ 2 0 1 0 CEA ASSAY Forest, J . C , Mass~, J., L~vesque, C. and Pelletier, L., Service de biochimie, Pavillon Saint-FranAois d'Assise, CHUQ, Quebec, QC, G I L 3L5, C a n a d a
The Elecsys ® CEA assay is based on a double monoclonal antibody sandwich reaction with electrochemiluminescence detection. Objectives We evaluated the analytical performance of the Elecsys ® CEA assay (BMC, Montreal, QC). Methods Within r u n imprecision was evaluated on 3 serum pools with 21-fold determinations, one r u n per day, over three days. The zero calibrator was m e a s u r e d 21 times in 3 independent runs to estimate lower detection limit (LDL). Between-day imprecision was determined by m e a s u r i n g 3 serum pools over 21 runs. We compared the results of fresh samples with ES 300 (BMC, Montrdal, QC) and Axsym (Abbott, Mississauga, ON) assays. Results W i t h i n - r u n imprecision varied from 1.4 to 4.6% (mean pool levels of 4.9, 32.9 and 85.0 ~Lg/L). We obtained a LDL < 0.1 ~g/L. The between-run CVs ranged form 6.5 to 8.5% (mean pool levels of 5.3, 33.2 a n d 85.8 ~g/L). The Elecsys ® CEA assay showed good correlation with both comparative assays (r > 0.99, n = 110) but with negative proportional biases (slope of 0.705 and 0.765 in comparison with the Axsym and ES 300 assays respectively). The slope was n e a r e r to 1 for the 0 - 2 5 ~Lg/L concentration range (0.863 and 0.982 respectively, n = 88). Conclusions The Elecsys ® CEA assay demonstrates adequate precision and compares well with two existing methods in the 0 - 2 5 ~g/L concentration range.
26.
EVALUATION OF ELECSYS ® 2 0 1 0 PSA ASSAY Forest, J.C., Mass~, J., L~vesque, C and Pelletier, L., Service de biochimie, Pavillon Saint-FranAois d'Assise, CHUQ, Quebec, QC, G1L 3L5, C a n a d a
The Elecsys ® PSA assay uses a double monoclonal antibody sandwich reaction with electrochemi-luminescence detection. The assay shows equimolar reaction with free and bound PSA. Objectives We evaluated the analytical performance of the Elecsys ® PSA assay (BMC, Montr6al, QC). Methods Within r u n imprecision was evaluated on 3 serum pools with 21-fold determinations, one r u n per day, over three days. The zero calibrator was m e a s u r e d 21 times in 3 independent runs to estimate lower detection limit (LDL). Between-day imprecision was determined by m e a s u r i n g 3 serum pools over 21 runs. We compared the results of fresh samples with ES 300 (BMC, Montreal, QC) a n d Axsym (Abbott, Mississauga, ON) assays. Results W i t h i n - r u n imprecision varied from 0.5 to 3.5% (mean pool levels of 0.16, 4.9 and 25.5 ~g/L). We obtained a LDL of 0.007 ~g/L. The between-run CVs ranged from 5.2 to 13.4% (mean pool levels of 0.23, 5.0 a n d 30.4 ~g/L). The Elecsys ® PSA assay showed good correlation with both comparative assays (r > 0.99, n = 110) but with negative proportional biases (slope of 0.924 and 0.879 in comparison with the Axsym a n d ES 300 assays respectively). For the comparison with the ES 300 assay, the slope was n e a r e r to 1 in the 0 - 2 5 ~Lg/L concentration range (1.051, n = 93). Conclusion The Elecsys ® PSA assay is sensitive and shows acceptable precision. CLINICAL BIOCHEMISTRY, VOLUME 30, J U N E 1997
23.
AUTOMATED ANALYSIS OF URINARY OXALATE USING BMC OXALATE DECARBOXYLASEBASED A S S A Y KIT Chu, SY, Biochemistry Laboratory, Dr. E. Chalmers Hospital, Fredericton, N.B. E3B 5N5
Increased oxalate excretion is commonly associated with u r i n a r y calculi formation. Oxalate determination based on a n enzymatic assay system offers assay simplicity and reliability. Objectives 1) To investigate the optimum assay conditions of the BMC oxalate decarboxylase method for urine oxalate determination; 2) To develop a n automated procedure on the Cobas Mira using the BMC kit. Methods Oxalate is first cleaved to formic acid by oxalate decarboxylase a n d subsequently the formic acid is quantitatively oxidized to bicarbonate in the presence of formate dehydrogenase. The a m o u n t of NADH formed during the reaction is m e a s u r e d by a n increase of OD at 340 nm. Optimal incubation time was followed by OD change at 37 ° after fixed incubation period for either the first stage or final stage of the reaction. Automated assay p a r a m e t e r s were developed based on optimal incubation time, sample reagent ratio, linearity range and m a x i m u m recovery. Results Five m i n u t e incubation time for both enzymatic reactions was chosen. A sample reagent ratio of 1:10 was used. Sample b l a n k was required to correct for endogenous non-specific O.D. change. EDTA was also required to improve sample oxalate recovery and to minimize oxalate precipitation. A 3% CV was obtained in pair data study and 6% CV for between day imprecision study. Linearity up to 1200 ~Lmol/L was obtained. Conclusion We have adopted the BMC oxalate test kit to be r u n on the Cobas Mira offering a fast and reliable procedure for u r i n a r y oxalic acid determination.
24.
IMMULITE CHEMILUMINESCENT IMMUNOASSAY FOR PTH IN PEDIATRIC SAMPLES COMPARED TO NICHOLS INSTITUTE IMMUNORADIOMETRIC A S S A Y Abdelrahman, A:~ Wan, B., Grossi, A., Makela, S., and Ellis, G., Paediatric Laboratory Medicine, Hospital for Sick Children, 555 University Avenue, Toronto, ONT M5G 1X8, Canada
Objective To compare the performance of the IMMULITE chemiluminescent i m m u n o a s s a y (IMM) for serum parathyroid hormone (PTH) to the Nichols Institute (NI) assay. Methods S e r u m PTH levels were m e a s u r e d by both methods in all samples received over a five m o n t h period (n = 366). When t h e r e was a large difference between the PTH values obtained by the two methods, we reviewed the p a t i e n t chart. Results There was a good correlation between both methods (IMM = 7.9 + 1.04NI, r = 0.969), however t h e r e were some large differences between values m e a s u r e d by the two methods for some of the samples as shown in the table: PTH (ng/L), total calcium (Ca, mmol/L), ionized calcium (ion. Ca, mmol/L).
PTH (NI)
PTH (IMM)
Ca
Ion. Ca
Diagnosis
1
1
20
2.89
1.26
Idiopathic hypercalcemia
2
22
981
2.54
1.17
Partial DiGeorge
3
2
22
2.77
NA
Hypercalcemia
4
10
36
2.55
1.09
Mild Partial DiGeorge
5
15
159
2.33
1.16
Developmental delay
6
32
5
2.74
1.28
E n d stage renal disease
374
Conclusions The exact reason for these differences in PTH values between the two methods was not clear even after reviewing the patients charts. However, caution m u s t be used when interpreting PTH results for some pediatric samples.
25.
EVALUATION OF ELECSYS--~ 2 0 1 0 CEA ASSAY Forest, J . C , Mass~, J., L~vesque, C. and Pelletier, L., Service de biochimie, Pavillon Saint-FranAois d'Assise, CHUQ, Quebec, QC, G I L 3L5, C a n a d a
The Elecsys ® CEA assay is based on a double monoclonal antibody sandwich reaction with electrochemiluminescence detection. Objectives We evaluated the analytical performance of the Elecsys ® CEA assay (BMC, Montreal, QC). Methods Within r u n imprecision was evaluated on 3 serum pools with 21-fold determinations, one r u n per day, over three days. The zero calibrator was m e a s u r e d 21 times in 3 independent runs to estimate lower detection limit (LDL). Between-day imprecision was determined by m e a s u r i n g 3 serum pools over 21 runs. We compared the results of fresh samples with ES 300 (BMC, Montrdal, QC) and Axsym (Abbott, Mississauga, ON) assays. Results W i t h i n - r u n imprecision varied from 1.4 to 4.6% (mean pool levels of 4.9, 32.9 and 85.0 ~Lg/L). We obtained a LDL < 0.1 ~g/L. The between-run CVs ranged form 6.5 to 8.5% (mean pool levels of 5.3, 33.2 a n d 85.8 ~g/L). The Elecsys ® CEA assay showed good correlation with both comparative assays (r > 0.99, n = 110) but with negative proportional biases (slope of 0.705 and 0.765 in comparison with the Axsym and ES 300 assays respectively). The slope was n e a r e r to 1 for the 0 - 2 5 ~Lg/L concentration range (0.863 and 0.982 respectively, n = 88). Conclusions The Elecsys ® CEA assay demonstrates adequate precision and compares well with two existing methods in the 0 - 2 5 ~g/L concentration range.
26.
EVALUATION OF ELECSYS ® 2 0 1 0 PSA ASSAY Forest, J.C., Mass~, J., L~vesque, C and Pelletier, L., Service de biochimie, Pavillon Saint-FranAois d'Assise, CHUQ, Quebec, QC, G1L 3L5, C a n a d a
The Elecsys ® PSA assay uses a double monoclonal antibody sandwich reaction with electrochemi-luminescence detection. The assay shows equimolar reaction with free and bound PSA. Objectives We evaluated the analytical performance of the Elecsys ® PSA assay (BMC, Montr6al, QC). Methods Within r u n imprecision was evaluated on 3 serum pools with 21-fold determinations, one r u n per day, over three days. The zero calibrator was m e a s u r e d 21 times in 3 independent runs to estimate lower detection limit (LDL). Between-day imprecision was determined by m e a s u r i n g 3 serum pools over 21 runs. We compared the results of fresh samples with ES 300 (BMC, Montreal, QC) a n d Axsym (Abbott, Mississauga, ON) assays. Results W i t h i n - r u n imprecision varied from 0.5 to 3.5% (mean pool levels of 0.16, 4.9 and 25.5 ~g/L). We obtained a LDL of 0.007 ~g/L. The between-run CVs ranged from 5.2 to 13.4% (mean pool levels of 0.23, 5.0 a n d 30.4 ~g/L). The Elecsys ® PSA assay showed good correlation with both comparative assays (r > 0.99, n = 110) but with negative proportional biases (slope of 0.924 and 0.879 in comparison with the Axsym a n d ES 300 assays respectively). For the comparison with the ES 300 assay, the slope was n e a r e r to 1 in the 0 - 2 5 ~Lg/L concentration range (1.051, n = 93). Conclusion The Elecsys ® PSA assay is sensitive and shows acceptable precision. CLINICAL BIOCHEMISTRY, VOLUME 30, J U N E 1997